The clock frequency for commercial ICs (integrated circuit) is provided by a crystal oscillator (XTAL). However, different errors occur in frequencies of clock signals provided by the XTAL due to variant temperatures. Particularly, a Global Positioning System (GPS) receiver needs an accurate clock frequency for acquisition and tracking. Referring to FIG. 1, an original relation of the temperature and the frequency offset for the XTAL is represented as a curve S1. It is to be noted that, a common XTAL has a frequency variance of as high as 15 to 30 ppm (parts per million) under a temperature range of −40˜85° C.
Therefore, in a high accuracy GPS receiver, a temperature-compensated crystal oscillator (TCXO) is implemented to provide compensated clock signals in conjunction with temperature change. However, a TCXO, having a frequency stability of 0.5 ppm over the operational temperature range, may cost up to many times of that of a common XTAL, i.e., a non-TCXO, thus causing addition overall costs. In the view of the aforesaid issue, there is a need of a reliable, high accurate GPS receiver that can be effectively mass produced while saving the TCXO.